1. Field of the Invention
The present invention relates to a tracking and traversing control technique for an optical disk apparatus.
2. Description of the Prior Art
In an optical disk apparatus, while rotating an optical disk such as a CD or a DVD, an optical pickup irradiates the recording surface of the optical disk with a laser beam and receives a reflected light from the recording surface of the optical disk to read out data optically. The optical pickup of such an optical disk apparatus comprises a focusing actuator for moving the focus of a laser beam irradiated on the optical disk in the optical axis direction, and a tracking actuator for moving the laser beam in the radial direction of the optical disk. The optical disk apparatus also comprises a traversing mechanism for moving the optical pickup to a predetermined position on the recording surface of the optical disk, and performs a so-called seeking operation, where a laser beam is irradiated on a predetermined position on the recording surface of the optical disk by controlling the tracking actuator and the traversing mechanism. In a seeking operation, the optical disk apparatus is adapted to calculate the moving speed of the optical pickup based on the frequency with which the optical pickup traverses tracks and to control the moving speed to be a predetermined speed, where a method of detecting and feeding back the moving speed in a seeking operation for acceleration and deceleration control is frequently used as an example (refer to Japanese Patent Laid-Open Publication No. Hei 6-301989 for example). In such an optical disk apparatus, if the moving speed is slower than the predetermined speed, an acceleration control is applied to the tracking actuator and the traversing mechanism, while if the moving speed is faster than the predetermined speed, a deceleration control is applied to the tracking actuator and the traversing mechanism. Then, in the acceleration and deceleration control, a drive signal prescribed in accordance with the difference in speed is applied to spindle motors, respectively, in the tracking actuator and the traversing mechanism.
However, since optical pickups are constructed by assembling a plurality of electronic and optical components and thereby include individual differences by necessity, and tracking actuators also include individual differences due to the characteristics of coils, magnets, etc., in the case of applying a specific drive signal to a tracking actuator as in the above-mentioned prior art example, the amount of movement differs for each tracking actuator. That is, due to the characteristics of coils, magnets, etc., the ratio of the magnitude of a force that acts on a coil to an applied voltage value differs for each tracking actuator. This suffers from a trouble in that in the case of a tracking actuator in which a larger force is applied to a coil with respect to the applied voltage value, the position of laser beam passes by a desired position when the specific drive signal is applied, while in the case of a tracking actuator in which a smaller force is applied to a coil with respect to the applied voltage value, the position of laser beam does not reach a desired position even when the specific drive signal is applied.